FDA Approves Scholar Rock's SMA Drug Isembyld, Stock Jumps 9% After Year-Long Manufacturing Delay

The FDA approved Scholar Rock's apitegromab, sold under the brand name Isembyld, on Friday, September 11, 2026, clearing the drug for adults and children age 2 and older with spinal muscular atrophy who are already on an SMN2-targeted therapy like Biogen's Spinraza or Roche's Evrysdi, according to the FDA's own approval announcement.

The agency calls it the first therapy for SMA that directly targets muscle loss rather than the underlying genetic defect. Isembyld is designed to work alongside those existing drugs, not replace them.

Scholar Rock Holding Corp (NASDAQ: SRRK) shares rose 9.1% in premarket trading Monday to $60.45, according to Yahoo Finance and Investors Hub, putting the stock near its 52-week high of $61.76. That's a long way from the roughly $10 a share the stock traded at for years before its late-2024 trial results, as BiopharmGuy Dive noted.

What the Data Show

The approval rests on the Phase 3 SAPPHIRE trial, which enrolled 188 participants ages 2 to 21 who could not walk or move independently, all of them already on an approved SMN2 drug, according to the FDA. The primary analysis covered 156 patients ages 2 to 12.

Patients on the 10 mg/kg dose of Isembyld showed a statistically significant improvement in motor function after one year, measured by the 33-point Hammersmith Functional Motor Scale Expanded, while the placebo group declined, the FDA said. Treated patients were more than twice as likely to hit a clinically meaningful improvement threshold: 34.2% versus 13.5% on placebo.

The most common side effects were upper respiratory infections, vomiting, cough and headache. The FDA also flagged an increased fracture risk, with BioSpace reporting fractures in 9% of patients on the lower dose versus 2% on placebo. Isembyld does not carry a boxed warning.

A Rocky Road to Approval

This wasn't a straight line. Scholar Rock first filed for approval in 2025 and got rejected, with the FDA citing compliance problems at a fill-finish manufacturing site in Indiana, then owned by Novo Holdings after its $16.5 billion buyout of Catalent in 2024, according to BioSpace and Pharmaphorum.

The FDA gave that plant an Official Action Indicated classification this spring, prompting Scholar Rock to drop the site from its application entirely in August and swap in an alternate facility, BioSpace reported. That forced the company to refile in Europe as well. Friday's approval came weeks ahead of the original September 30, 2026 PDUFA deadline, according to BioSpace.

Price Tag and Market Reaction

BiopharmGuy Dive reported that Scholar Rock executives disclosed an annual list price of about $310,000 for a typical SMA patient on a Monday investor call, with actual costs varying by patient weight and insurance coverage. That price had not been made public as of the approval announcement, according to Pharmaphorum.

Wall Street moved fast. Truist Securities raised its price target to $76 from $55, keeping a Buy rating. Raymond James lifted its target to $72 from $65, forecasting apitegromab revenue of roughly $2.2 billion by 2035. Citi raised its target to $74 from $60. Scholar Rock now carries 18 Buy ratings and zero Hold or Sell ratings among covering analysts, according to Yahoo Finance and Investors Hub. BMO Capital Markets separately projected peak sales between $2.1 billion and $2.3 billion, a figure both BioSpace and Pharmaphorum attributed to the firm.

Scholar Rock says it has two independent fill-finish facilities now and about $492 million in cash on hand heading into commercial launch, per Yahoo Finance.

A $310,000-a-year price tag for a chronic add-on therapy, not a cure, is the kind of number that draws scrutiny from insurers and patient-cost advocates, especially layered on top of existing SMN2 drug costs patients are already paying. None of the sources here include a payer or insurer response to the pricing, and Scholar Rock has not detailed a patient assistance framework beyond stating its "Scholar Rock Supports" team is standing up assistance for patients and caregivers, according to the company's own announcement.

Cure SMA president Kenneth Hobby called the approval "a significant turning point" for a patient population that has "been waiting for innovative therapeutic options to improve motor function," per the company's release, which also carried a statement from CEO David Hallal calling it "a defining moment for the SMA community."

Scholar Rock says Isembyld will ship "in the coming days." The approval also earned the company a rare pediatric disease priority review voucher, which Pharmaphorum noted can be used to speed FDA review of a future drug application. Whether payers push back on the $310,000 list price, and how quickly physicians actually prescribe the drug alongside existing SMN2 therapies, will determine whether Wall Street's $2 billion-plus sales forecasts hold up.